Preparation of organo-lithium compounds in the presence of conjugated hydrocarbon dienes



United States Patent 3,392,202 PREPARATION OF ORGANO-LITHIUM COM- POUNDSIN THE PRESENCE OF CONJU- GATED HYDROCARBON DIENES Ervin G. Pritchett,Cincinnati, Ohio, assiguor to National Distillers and ChemicalCorporation, New York, N.Y., a corporation of Virginia No Drawing.Continuation-impart of application Ser. No. 294,762, July 12, 1963. Thisapplication Oct. 24, 1963, Ser. No. 318,504

13 Claims. (Cl. 260-665) This application is a continuation-in-part ofcopending application Ser. No. 294,762, filed July 12, 1963, now PatentNo. 3,308,110.

The invention relates to an improved process for polymerizing activeconjugated dienes. More particularly, the invention relates to animproved catalyst for a process for producing from conjugated dienespolymers having low vinyl unsaturation.

It is known that active conjugated dienes can be polymerized to polymershaving low vinyl unsaturation using as a catalyst an organolithiumcompound or lithium metal. that yields organolithium intermediates. Suchpolymerization, however, is unsatisfactory because the rate isundesirably slow below about 60 C. While polymerization rates increasewtih increasing temperature, at temperatures above about 60 C. theorganolithium compound or intermediate undergoes decomposition. This isa disadvantage when high molecular weight linear products with narrowmolecular weight distributions are sought or when the product polymersare to be terminated by functional groups via displacement of theterminal lithium.

It is known in the art that the presence of ether in the reaction mediumincreases the rate of polymerization of conjugated dienes; however, as aconsequence of the presence of even small amounts of ether, there is asubstantial loss of polymer linearity. Attempts to increase dienepolymerization rates without loss of polymer linearity by modifying theorganolithium catalyst, for example by addition of a hindered tertiaryamine, also have serious disadvantages, among these being an inducedloss of active terminal organolithium from the growing polymer chains.

It is an object of this invention to provide an improved catalyst forthe polymerization of active conjugated dienes to polymers having lowvinyl unsaturation by a process that overcomes the disadvantages of theprocesses of the prior art.

It is a further object of this invention to provide a novel process forthe preparation and stabilization of organolithium compounds.

It is also an object of this invention to provide an improved processfor introducing, in a wholly hydrocarbon medium, lithium ontolithium-receptive unsaturated organic compounds.

A still further object of this invention is to provide high puritydilithio compounds in wholly hydrocarbon diluent.

Additional objects will become apparent from the following detaileddescription.

In the copending application it was shown that active conjugated dienescan be rapidly polymerized to low vinyl (high 1,4-addition) polymerswhile maintaining complete activity of the anionic terminal lithium tosubsequent reaction by using as catalyst a combination of anon-polymerizable diene and lithium metal or an organolithium compound.The polymerization rate is increased significantly without the usualconcomitant side effects of increased molecular weight, wider molecularweight distribution, and loss of reactive lithium chain ends. The

3,392,202 Patented July 9, 1968 process is particularly useful for theproduction of linear or stereoregular rubbers or for the production ofhighly linear functionalized polymers such as hydroxyl-terminated lineardienes. I

The combination of 1) diene that is non-polymerizable via lithium ororganolithium catalysis and (2) lithium metal or an organolithiumcompound is an exceptionally effective catalyst for the polymerizationof anionically polymerizable conjugated dienes, said polymerizationtaking place essentially by 1,4-addition and resulting in liquids orrubbery solids having low vinyl content. The non-polymerizable dieneportion (1) of the catalyst does not react with the lithium metal ororganolithium compound portion (2) ,nor does it copolymerize with thepolymerizable dienes, thus making it possible and convenient to recoverthe non-polymerizable diene from the polymerization mixture.

In carrying out the process the polymerizable conjugated diene, e.g.,butadiene or isoprene, is contacted with the combination catalyst atnormal temperatures and pressures by any convenient method. Preferably amixture of the non-polymerizing diene and the lithium or organolithiumcompound is injected as a precombined catalyst combination into aprocess stream consisting of the polymerizable diene monomer in an inertliquid dilucut at normal or slightly elevated temperature and undersufficient pressure to retain the monomer in solution. The temperatureand pressure are maintained until the desired degree of polymerizationis achieved; the reaction is then terminated. It is also possible toadapt this procedure to a batch or semi-batch operation.

Other possible modes of contacting the monomer with the catalyst include(1) injecting the organolithium compound into a mixture of thepolymerizable and nonpolymerizing dienes and (2) adding thepolymerizable diene to a solution or suspension of the combinationcatalyst in an inert diluent.

The polymerization process is preferably, although not necessarily,carried out in the presence of an inert liquid reaction medium. Examplesinclude aliphatic and aromatic hydrocarbons, such as pentane, hexane,heptane, heptene-l, isooctane, cyclohexene, cyclohexane, benzene,toluene, xylene, etc.; alkylate; and the like; and mixtures thereof. Theamount of diluent may range up to about 20 parts by weight per part ofpolymer; preferably the range is between about 1 to 6 parts.

It is necessaryin carrying out the process that all of the materialsused be free of substances that can destroy the organolithium compound,e.g., water; carbon dioxide; oxygen; compounds containing activehydrogen, such as alcohols, esters, primary and secondaryaminescontaining -NH groups; and the like; that tend to decrease polymerlinearity, e.g., ethers; or that tend to destroy polymer functionality,e.g., tertiary amines. The reaction is carried out preferably in anatmosphere of nitrogen or other inert gas, such as argon or helium.

The process is particularly applicable to the polymerization ofbutadiene and of isoprene, but it applies equally to other activeconjugated dienes, such as pentadiene-1,3, 2,3-diphenylbutadiene-1,3,2,3-dimethyl-1,3J-butadiene, 2- chloro-l,3-butadiene, 2,3-dichloro-1,3butadiene, 2,4-hexadiene, chloro-fluoro-LS-butadiene, and mixtures ofthese dienes with each other or with other monomers copolymerizabletherewith, as for example aliphatic diolefins, styrene, substitutedstyrenes, methacrylate esters, e.g., methyl methacrylate, ordivinylbenzene.

The non-polymerizing diene portion of the catalyst is a hydrocarbondiene of the empirical formula C H or C H J wherein n is an integerranging from 5 to about 3 30 and which has one of the following carbonchain structures:

Type III Preferred is a 2,5-dialkylhexadiene-2,4 (Type I), especially2,5-dimethylhexadiene-2,4. Other dienes not readily polymerized byorganolithium compounds, however, also can be used, such as2,5-dimethylhexadiene-l,5 (Type III), 1,4-dimethylenecyclohexane '(TypeIII, cyclic), cyclohexadiene-1,3 (Type I, cyclic), 1,4-pentadiene (TypeII), 1,4- dihydrobenzene (Type II, cyclic), and the like, or mixturesthereof. These dienes may be purified satisfactorily for the purposes ofthis process by con-tact with a molecular sieve or by distillation froman organolithium compound.

The organolithium portion of the catalyst can be any alkyl, alkaryl, orcycloalkyl lithium, such as for ex ample butyl lithium, propyl lithium,isobutyl lithium, amyl lithium, cyclohexyl lithium, phenyl ethyllithium, dilithiopentane, dilithionaphthalene, and the like, or mixturesthereof. It is known that certain organolithium compounds can beprepared in wholly hydrocarbon solvent by reacting lithium metal withthe corresponding organohalide. The

tendency toward coupling reactions with the organoha-lide,

however, requires the use of large excesses of lithium; consequently,yields are reduced to an extent particularly undesirable in thepreparation of dilithio compounds. Previous attempts to prepareorganolithium compounds by the direct addition of lithium to unsaturatedorganic compounds in wholly hydrocarbon solvent have been unsuccessfulfor several reasons including (a) very slow addition rates of lithium,(b) very low conversion to the organolithium compound, and poorstability of the products. The art specifically stresses the requirementfor the use of active ethers as solvents or partial solvents in the.addition reaction of alkali metals to active hydrocarbons; this is amajor disadvantage because the removal of such ethers from theorganolithium products is extremely difficult.

It has now been found that lithium metal can be added to activehydrocarbons in a wholly hydrocarbon diluent at reasonable reactionrates and with high conversions by intimately contacting lithium metalwith an organic compound active to lithium addition in the presence of anon-reactive diene hydrocarbon catalyst as described above. The lithiummetal is mixed intimately with the organic compound active to lithiumaddition and with the non-reactive diene hydrocarbon catalyst untilessentially complete conversion of the active hydrocarbon toorganolithium has taken place. To stabilize organolithium compounds, thenon-reactive diene can be added to an organolithium compound in ahydrocarbon medium previously prepared by any convenient means.

The organic compound active to lithium addition can be any organiccompound that contains unsaturation active to the addition of alkalimetals. More specifically, it is an organic compound containingunsaturation activated by adjacent vinyl or aromatic groups and one thatis active to alkali metal addition in ether diluents. Examples of suchactive organic compounds include naphthalene, hiphenyl, .anthracene,dimethylfulvene, 1,1-diphenylethylene, stilbene, tetraphenylethylene,2,6-dimethyl-4-methylene-heptadiene-2,5, 2-phenylpropene-1,9-furalfulvene, 1, 1,3,3-tetraphenylallene, 1,1,3-triphenylpropene-2,benzophenone anil, benzylidene aniline, acridine, acetophenone ketazine,benzophenone hydrazone, .azobenzene, styrene oxide, and the like, andmixtures thereof. Of these active compounds, the preferred ones forlithio addition products to be used subsequently in 1,4-type dienepolymerizations are completely hydrocarbon, i.e., those that are free ofatoms other than carbon and hydrogen.

The dilithio compounds produced by the process of this invention aresolids that are only slightly soluble in hydrocarbons. It is preferred,but not essential, that they be in the form of time suspensions in thenon-reactive diene hydrocarbon catalyst or, more preferably, in amixture of the non-reactive diene .and an inert hydrocarbon diluent.Suitable inert diluents are aliphatic, aromatic, or arylaliphatichydrocarbons, examples of which include pentane, hexane, heptane,cyclohexane, benzene, toluene, xylene, refined kerosene, and the like,and mixtures of these.

Although it is not necessary, in order to obtain optimum reaction ratesin the addition of lithium to active unsaturated compounds, the metal ismixed with the unsaturated compound by grinding. Any suitable means maybe employed; for example, a ball mill equipped with steel balls or rodsor a stirred vessel known as an attritor may be used. It is alsopossible to use other means of violent agitation, such as an ultrasonicmixer, in any suitable vessel.

As stated above, in order to prevent reactions with impurities, allreaction vessels, grinding balls, mixing equipmerit, and the like thatcontact the reactants should be thoroughly dry and protected by an inertatmosphere such as nitrogen, argon, helium, or the like.

Fine suspensions of dilithium product easily transferable in a fluidstate are produced by having the dilithium product within theconcentration range of about 0.01 to 2.0 grams of lithium per parts ofdiluent; preferably the amount of lithium ranges from about 0.05 to 1.0gram per 100 parts of diluent.

The amount of the non-reactive hydrocarbon diene catalyst can vary fromabout 0.01 up to about 10,000 parts per part of lithium, the use of thenon-reactive diene catalyst as diluent not being excluded. It ispreferred, however, to use from about 0.05 up to about 100 parts of thenon-reactive diene per part of lithium or, in other words, from about0.1 to about 5 moles of non-reactive diene catalyst per equivalent oflithium.

The temperature at which the lithium is added to the lithium-receptiveunsaturated organic compound can range from about 30 up to about 100 C.,and the temperature employed is preferably between about 0 and 60 C.

The stable high purity dilithio compounds in wholly hydrocarbon diluentprepared by the process of this invention are useful in thepolymerization of polymerizable diene hydrocarbons to linear (low vinylunsaturation) polymers such as cis-polyisoprene rubber. The dilithiocompounds are useful also in the manufacture of block and graftcopolymers of polymerizable diene hydrocarbons, styrenes, acrylate andmethacrylate esters, and the like. They are particularly useful in thepreparation of dihydroxyl-terminated polydienes having vinyl to internalunsaturation ratios of one or less, as disclosed in copendingapplication Ser. No. 305,227 (filed Aug. 28, 1963), now Patent No.3,308,170, issued Mar. 7, 1967.

The concentration of total catalyst can range from about 0.001 up toabout 10 mole percent, based on the weight of the polymerizable diene.High molecular weight rubbers are produced at the lower catalystconcentrations, whereas useful oils or functionalized fluid polymers areproduced at higher catalyst levels. A range of from about 0.01 to about5 mole percent is preferred.

The polymerization temperature in general can range from about -20 up toabout 100 C., but a temperature between about 25 and about 60 C. ispreferred. The preferred pressure range is between about 1 and about 2atmospheres, although it is possible to employ a pressure between lessthan 1 and up to about 9 atmospheres.

The resulting polymers are valuable as raw materials for plastics,rubbers, foams, coatings, and the like. Particularly valuable are thecarboxyl and hydroxyl compounds which are obtained when thelithium-terminated polymers are reacted with suitable compounds, such ascarbon dioxide or an epoxide, for example, an aliphatic epoxide such asethylene oxide, propylene oxide, or the butylene oxides or an aromaticepoxide such as styrene oxide. The reactant may also be a suitablecarbonyl-type compound, such as for example aldehydes, such asformaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde,butyraldehyde, isobutyraldehyde, and the octylaldehydes, e.g.,2-ethylhexaldehyde. Aromatic and heterocyclic aldehydes such asbenzaldehyde and furfural can also be used, a can such aldehydes assalicylaldehyde, anisaldehyde, cinnamaldehyde, piperonal, vanillin,acrolein, and crotonaldehyde. Carbonyl compounds of the ketone classalso can be employed, for example, acetone, methyl ethyl ketone, diethylketone, acetophenone, benzophenone, methyl vinyl ketone, mesityl oxide,phorone, and benzoquinone. It is also possible to produce hydroxylcompounds from the lithium-terminated polymers by oxidizing them withoxygen itself, either as pure oxygen or admixed with inert materials,such as in dry air. Ozone also can be used as well as oxidizingmaterials that yield oxygen or its oxidizing equivalents. These includesodium peroxide, hydrogen peroxide, the persulfates, and other organicand inorganic peroxides, metal peroxides, nitrogen oxides,nitro-aromatic compounds such as nitrobenzene, and some metal salts.

At least one equivalent of the hydroxyl-forming reactant is required foreach lithium equivalent of the polymer, and in order to insure completereaction an excess of the reactant is usually employed. When using anepoxide, for example, the excess may be up to about 500 percent; it ispreferably from about percent up to about 150 percent.

The reaction with the hydroxyl-forming compound, for example as in thecase of using an epoxide, is followed by treating the lithium salts ofthe resulting corresponding hydroxyl compounds with a hydrolyzing agent,e.g., water, an alcohol such as methanol or ethanol, etc., to destroyany unreacted lithium and to liberate the hydroxyl compounds from theirlithium derivatives that are initially formed. The hydroxyl compoundsare isolated from this reaction mixture by extraction, distillation, orother suitable means.

The reaction of the polymer with the appropriate hydroxylorcarboxyl-forming compound is generally carried out at a temperaturebetween about the reflux temperature of the selected reaction medium andabout 60 C. or lower; the temperature is preferably between about thereflux temperature and about 40 C.

Here too it is important that the presence of moisture and compoundscontaining active hydrogen be carefully controlled in order to preventpremature loss of terminal lithium groups. It is also necessary thatother reactive materials be excluded; therefore, the reaction should beconducted in an inert atmosphere such as nitrogen, argon, helium, or thelike.

Other than being treated to produce polymeric acids or alcohols asaforedescribed, the polymers can be reacted with other compounds to givea wide range of products. For example, they can be reacted with aGrignard-type reactant having carbonyl, thionyl, or nitrile groups.Typical examples of such reactants are sulfur dioxide, benzene sulfonylchloride, thionyl chloride, acetonitrile, propionitrile, and the like.In addition, reactions with halides, dihalides, trihalides, andtetrahalides, particularly chlorides, bromides, and iodides, aresuitable, as are reactions with organic compounds such as alkylaryl,acetylenic, nitrile, and cyclodienyl compounds and reactions withcombinations of the above reactants.

Although the utility of the organolithium compounds of the presentinvention is being illustrated with the formation of di-functionalpolydienes, it is not intended to limit their utility thereto.

In the following examples analyses of reaction mixtures were derived bycombining the results of two operations which determined (a) unreactedlithium and (b) total alkali. Unreacted lithium generally was measuredby decomposing a suitable-sized sample of the reaction mixture with drybutyl Cellosolve (ethylene glycol monobutyl ether) in an oil-sealedgasometer which measured up to 50 ml. of evolved hydrogen to an accuracyof about 0.02 ml. Following the measurement of the evolved hydrogen, thealcohol-decomposed sample was titrated to the phenolphthalein end pointwith 0.1 N sulfuric acid. Unreacted lithium was defined by L=vfg/ 11.2Gmilliequivalents where L is unreacted lithium, v is milliliters ofevolved hydrogen, g is grams of sample, G is grams of total reactionmixture, and f is a factor for reducing v to normal conditions (0 C. and760 mm.). The factor 1 may be found tabulated in Langes Handbook ofChemistry (Handbook Publishers Inc., Sandusky, Ohio).

Total alkali (T) was defined by T: VNg/ G milliequivalents where V ismilliliters, N is the exact normality of the titrating acid, g is gramsof sample, and G is grams of total reaction mixture; thus both L and Tare defined by the identical sample.

In some cases L was determined by the known Gilman- Haubein titration,and such values are so designated where used. This method is notpreferred, however, because it requires separate samples for thedetermination of L and of T.

From the values of L and T various values describing the completion ofreaction at any time 2 between lithium and a reactive hydrocarbon or anorganohalide can be derived. In the following equations a is (11) molesof hydrocarbon which can add two milliequivalents of lithium or (2)milliequivalents of organohalide reactant; 2a+c is milliequivalents oflithium; and n is a or (2a+c)/2, whichever is smaller; all are at t=0.Thus at time t:

Percent of theory Li used= X Percent of theory C-Li bonds f0rmed=Percent of theory R-X used= X 100 and Percent of theory R-X lost toWurtz reaction:

The utility of these analyses and derived values will be apparent in thefollowing examples in which, unless otherwise specified, all parts areby weight and all reactions took place at ambient temperature. It is tobe understood that these examples are for purposes of illustration andnot for limitation.

EXAMPLE I Reactors were 8-ounce glass bottles containing about 480 parts(about 40 volume percent) of Asa-inch stainless steel grinding balls.Each bottle was sealed by a neoprene disc held firmly in place with apunctured metal screw cap. The reactors were thoroughly oven-dried priorto use and were swept with dry argon while cooling. Reactants anddiluent were entered, the reactors were sealed while an argon atmospherewas maintained, and milling was accomplished by rotating the reactors at100 r.p.m. about the vertical axes. Samples for analysis were withdrawninto suitable hypodermic syringes for transfer.

In a series of runs each using 0.423 part of lithium metal as a 30percent dispersion in parafiin. wax and 5.40 parts ofscintillation-grade trans-stilbene, the reactants were milled togetherin a total of 50 parts by volume of the diluents shown in Table 1 forthe length of time given and then analyzed.

TABLE 1.ADDITION OF LITHIUM TO STILBENE 2 TMB l (100) 1 TMB=2,5-dimethylhexadienc-2,4.

2 Second analysis by GilmamHaubein method.

From the above data it is evident that in the presence of2,5-dimethylhexadiene-2,4 the rate of reaction of a compound active tothe addition of lithium is increased.

EXAMPLE II 0.457 part of lithium metal as a dispersion in paraffin waxand 5.405 parts of trans-stilbene were milled together as in Example I,using as diluent a mixture of 51 parts of n-heptane and 20 parts of2,5-dimethylhexadiene-2,4. Within 20 hours 99.5 percent of theorylithium had reacted. The reaction mixture, a thick black suspension, wastransferred to a stirred, round-bottom flask and further reacted with 5parts of ethanol. 25 parts of water was added, the mixture was acidifiedto pH 1 with concentrated hydrochloric acid, and the organic layer waswashed with water to pH 6 and dried over calcium sulfate. Uponevaporation of the organic diluent, 5.33 parts (95 percent) of slightlydamp crystals melting at 5054 C. remained. Recrystallization fromacetone-water gave 1,2-diphenylethane; melting point alone and mixedwith an authentic sample was 54 C.

EXAMPLE III In each of two runs 0.437 part of lithium metal as adispersion in paraffin wax and 3.842 parts of naphthalene (twicerecrystallized from ethanol and thoroughly vacuum-dried) were milled asin Example I. In one run 68 parts of n-heptane was used as the diluent;in the other run a mixture of 51 parts of n-heptane and 20 parts of2,5-dimethylhexadiene-2,4 was used. Samples were removed at varioustimes for analyses. The results are given in Table 2.

TABLE 2.RELATIVE STABILITY OF DILITI-IIONAPHTHALENE IN HYDROCARBONS lTMB =2,5-din1cthylhexradium-2,4.

In the absence of 2,5-dimethylhexadiene-2,4 the dilithionaphthaleneinitially formed was unstable and an apparent reaction of only 2 percentresulted after 246 hours. 'In the presence of 2,5-dimethylhexadiene-2,4the dilithionaphthalene was formed in nearly quantitative yield and wasstable.

EXAMPLE IV 0.437 part of lithium metal as a dispersion in paraflin waxand 3.842 parts of naphthalene were milled as in Example 'I, using amixture of 65 parts of benzene and 20 parts of2,5-dirnethylhexadiene-2,4 as diluent. In 5 hours 85.9 percent reactionhad occurred; in 23 hours, 95.4 percent.

EXAMPLE V 0.44 part of an alloy of 1 percent of sodium in lithium metaldispersed in parafiin wax and 3.842 parts of naphthalene were milled asin Example I, using as diluent a mixture of 51 parts of n-heptane and 20parts of 2,5-dimethylhexadiene-2,4. In 5 hours 95.5 percent of thetheoretical alkali metal alloy had reacted.

EXAMPLE VI The procedure of Example I was repeated using 0.456 part oflithium metal as a dispersion in paraffin wax and 3.845 parts ofnaphthalene reactant. The diluent was a mixture of 51 parts of n-heptaneand 20 parts of 2,5- dimethylhexadiene-2,4. After 24 hours milling time,analysis indicated 93.5 percent reaction. The product was furtherreacted with ethanol as in Example II, but the dried organic layer wasconcentrated by distillation to about 15 percent solids. This solutionwas compared in vapor pressure chromatography with one ofdihydronaphthalene prepared by the known sodium-alcohol reduction ofnaphthalene. Dihydronaphthalene prepared via the lithium derivative ofthis example analyzed for 62.3 percent of 1,4- and 36.4 percent of1,2-dihydronaphthalene.

EXAMPLE VII The procedure of Example I was repeated using 0.208 part oflithium metal as a dispersion in paraffin wax and 5.45 parts of1,1-diphenylethylene. The diluent was a mixture of 13.6 parts ofn-heptane and 15.4 parts of 2,5-dimethylhexadiene-ZA. In 25 hoursmilling time 75 percent of the lithium had reacted.

EXAMPLE VIII 0.421 part of lithium metal as a dispersion in paraffinwax, 3.61 parts of styrene oxide, and 0.011 part of transstilbene (toreduce the time of initiation of the reaction) together with a mixtureof 30 parts of n-heptane and 3.8 parts of 2,5-dimethylhex-adiene-2,4 asdiluent were milled as in Example I. The reaction started in about 4hours, as evidenced by color formation. After 24 hours milling time theresulting brown suspension was sampled and analyzed. 89.2 percent of thetheoretical reaction of lithium had taken place.

EXAMPLE IX 0.455 part of lithium metal and 5.752 parts of a20- benzenewere mixed with 51 parts of n-heptane and 20 parts of2,5-dimethylhexadiene-2,4 and milled. Analysis of the resulting greensuspension at 24, 41, and 96 hours showed the completion of reaction atthese times to have been 89.1, 92.5, and 96.5 percent, respectively. Theproduct was further reacted with ethanol, washed with acid and Water,and isolated by evaporation by the method of Example II, the productbeing protected by a nitrogen atmosphere. 5.05 parts (100 percent) ofcrude product melting at -125 C. was recovered. Recrystallization fromethanol gave hydrazobenzene, M.P. 127 C., a white solid which darkenedin air.

EXAMPLE X 0.417 part of lithium metal as -a dispersion in paraflin waxand 5.40 parts of trans-stilbene were milled as in Example I, using asdiluent :a mixture of 54.5 parts of n-heptane and 16.5 parts of2,5-dimethylhexadiene-1,5 (n =1.429l). Within 12 hours 92 percent of thelithium metal had reacted.

EXAMPLE XI To illustrate that the rate of addition of lithium metal toactive hydrocarbons can be adjusted by the choice of hydrocarbondiluent-catalyst combination, four runs were made. In each run 0.43 partof lithium metal as a dis persion in parafiin wax and 5.40 parts oftrans-stilbene 9. were milled as in Example I, using the diluents andobtaining results as follows:

9 2,5-dimethylhexadiene-2,4 (17.1) L. J

I Only 75 percent reaction had occurred at 200 hours.

EXAMPLE XII To illustrate the utility of added non-polymerizing dienesas stabilizers for organolithium formed by methods other than the directaddition of lithium metal to compounds containing activated olefinicunsaturation, the following runs were made:

In each of two runs 0.415 part of lithium metal as a dispersion inparafiin wax and 2.12 parts of pentamethylene dichloride were milled inbottle reactors as described in Example I.

The diluent for run 13 was 37 parts of n-heptane and for run 14, amixture of 37 parts of n-heptane and 0.38 part of2,5-dimethylhexadiene-2,4. Analytical results at various milling times,using the Gilman-Haubein method, are presented in Table 4.

TABLE 4.-STABILIZATION OF PENTAMETHYLENE DILITHIUM Milling Time, hoursRun Analysis for percent of- 13 Li used- 48. 9 60.4 51. C-Li bondsformed 33.0 17. 3 0. 8 64. 7 103. 0 96. 5 31. 7 86. 0 95. 7 63. 3 55. 456. 0 44. 8 11. 7 12. 3 61. 5 99. 0 100. 0 16. 8 87. 5 88. 0

EXAMPLE XIII The utility of the lithio compounds in wholly hydrocarbondiluent is illustrated as follows:

Dilithionaphthalene was prepared as in Example IV, using 0.43 part oflithium metal, 3.842 parts of naphthalene, and a mixture of 51 parts ofn-heptane and 20 parts of 2,5-dimethylhexadiene-2,4. In 23 hours millingtime 92 percent addition reaction had occurred.

The dilithionaphthalene was transferred along with 68 parts of n-heptanerinse to a SOD-ml. round-bottom flask equipped with thermometer,high-speed stirrer, Dry Ice condenser, and inlets for argon andbutadiene. An argon atmosphere was maintained throughout. To thewellstirred dark-purple suspension was added 46.75 parts ofbutadiene-1,3 at about 50 C. and at such a rate that active reflux wasmaintained without lowering the temperature below 46 C. Duringpolymerization, partial precipitation of the polymer occurred, andstirring was difficult. At the end of the addition, a thickpolymersolvent mass was produced. The mixture was cooled to 20 C., 50parts by volume of cold 1,2-dimethoxyethane was added to thin and dilutethe mixture, and about 5 parts of liquid ethylene oxide was injected allat once 10 with rapidagitation. Within 1 solidified.

After overnight standing, about 20 parts of powdered Dry Ice was workedinto the reaction mixture, followed by 10 parts of ethanol whichfluidized the semi-solid mass. The mixture was acidified to pH 1 withaqueous oxalic acid, washed with water to pH 6, dried over anhydrouscalcium sulfate, and stabilized to oxidationwith 0.1 part oft-butyl'catechol. After filtration followed by evaporation ofvolatilesto 100 C./0.5 mm., there resulted 41.5 parts of a light yellowoil having a viscosity of 37 poises/25 C., a hydroxyl number of 44.92,an acid number of 1.46, and a ratio of vinyl to internal unsaturation of32 to 68 as determined by nuclear magnetic resonance (NMR) analysisusing the method of Hung Yu Chen (Anal. Chem. 34, 1134 (1962)).

' The glycol or difunctional nature of the product oil was demonstratedby mixing it with a 10 percent excess of toluene diisocyanate and curingthe mixture for 6 hours at 130 C. in an oven. The resulting polyurethaneelastomer had little tackiness and evidenced reasonable strength andelasticity when pulled by hand.

It should be noted that a polybutadiene glycol of equivalent molecularweight produced in an ether solvent would have about 60 to percent vinylunsaturation and viscosity of about 300 to 500 poises, whereas theproduct prepared in a wholly hydrocarbon medium by the process of thisinvention has only about 30 percent vinyl unsaturation and theremarkably low viscosity of 37 poises.

EXAMPLE XIV This example illustrates both the high activity obtainablewith non-polymerizing diene cocatalysts and the precautions necessary intheir use.

76.8 parts of 2,5-dimethylhexadiene-2,4 and 45.4 parts of butadiene-1,3were placed in a dry, argon-filled 8-ounce screw cap bottle at about 15C. The bottle was sealed with a neoprene disk under the screw cap. Whilethe contents were chilled, 0.2 part of butyl lithium as a 1.55 Nsolution in heptane was injected into the bottle which was thensubmerged and agitated in a 30 C. water bath behind a safety screen.After about 5 minutes the bottle exploded, depositing a solvent-wetpolymer mass into the bath and onto nearby surfaces, indicating thatpolymerization had occurred with extreme rapidity. At high cocatalystconcentrations it is, therefore, preferred to add monomer to thecatalyst-cocatalyst combination.

While there are above disclosed but a limited number of embodiments ofthe invention herein presented, it is possible to produce still otherembodiments without departing from the inventive concept hereindisclosed. It is desired, therefore, that only such limitations beimposed on the appended claims as are stated therein.

What is claimed is:

1. In a process for the preparation of organolithium compoundscomprising reacting lithium metal with an organic compound containingunsaturation active to lithium addition, the improvement comprisingconducting said reaction in the presence of a non-polymerizing,conjugated hydrocarbon diene.

2. The process of claim 1 wherein the non-polymerizing, conjugated,hydrocarbon diene has a formula selected from the group consisting of CH and C H wherein n is an integer ranging from 6 to about 30.

3. The process of claim 1 wherein the diene is a 2,5- dialkylhexadiene.

4. The process of claim 3 wherein the 2,5-dialkylhexadiene is2,5-dimethylhexadiene-2,4.

5. The process of claim 1 wherein the ratio of diene to lithium rangesfrom about 0.01 to about 10,000 parts of diene per part of lithium.

6. The process of claim 1 wherein the reaction temperature is in therange of about 30 C. to about C.

7. In a process for the preparation of organolithium to Zminutes, themixture compounds comprising reacting lithium metal with an organiccompound containing unsaturation active to lithium addition in thepresence of a hydrocarbon diluent, the improvement comprisingsubstituting for at least a portion of said hydrocarbon diluent anon-polymerizing, conjugated, hydrocarbon diene.

8. The process of claim 7 wherein the non-polymerizing, conjugated,hydrocarbon diene has a structural formula selected from the groupconsisting of C H and C H wherein n is an integer ranging from 6 toabout 30.

9. The process of claim 7 wherein the diene is a 2,5- dialkylhexadiene.

10. The process of claim 9 wherein the 2,5-dialkylhexadiene is2,5-dimethylhexadiene-2,4.

11. The process of claim 7 wherein the ratio of the diene to lithiumranges from about 0.01 to about 10,000 parts of diene per part oflithium.

12 12. The process of claim 7 wherein the reaction temperature is in therange of about 30 C. to about 100 C.

13. The process of claim 7 wherein the hydrocarbon 5 diluent is heptane.

References Cited UNITED STATES PATENTS 3,159,587 12/1964 Uraneck et al252431 10 2,559,947 7/1951 Crouch 260-94.2 3,055,952 9/1962 Goldberg260-665 TOBIAS E. LEVOW, Primary Examiner.

5 HELEN M. MCCARTHY, Examiner.

E. C. BARTLETT, A. P. DEMERS, Assistant Examiners.

1. IN A PROCESS FOR THE PREPARATION OF ORGANOLITHIUM COMPOUNDSCOMPRISING REACTING LITHIUM METAL WITH AN ORGANIC COMPOUND CONTAININGUNSTATURATION ACTIVE TO LITHIUM ADDTION, THE IMPROVEMENT COMPRISINGCONDUCTING SAID REACTION IN THE PRESENCE OF A NON-POLYMERIZING,CONJUGATED HYDROCARBON DIENE.